1. Field of the Invention
This invention relates to the manufacturing of wire harnesses, and more particularly to a method of and an apparatus for ensuring the amount of feed of wires in its manufacturing process.
2. Description of the Related Art
Electric devices in an automobile are electrically connected together by a wire harness. As shown in FIG. 10, a wire harness is formed by a method in which insulating sheathed wires a are arranged in a juxtaposed manner in a common plane, and the wires a are press-connected to connectors C at regions spaced along the length of the wires, and a lid T is fitted on and connected to each connector C.
In the manufacturing of such a wire harness W, the wires a are supplied to a processing zone where various processing, including the adjustment of the length of the wires, the installation of the wires, the cutting of the wires and the clamping of the wires to the connector C, are effected, and in these steps, the wires a have heretofore been fed, for example, by the following method. The construction and operation of this feed mechanism will be described with reference to FIG. 11.
The wire feed mechanism 115, shown in FIG. 11, includes two feed rollers 117 disposed on the lower side of the plurality of wires a, fed in a juxtaposed manner, to guide all of these wires a, and grooves 117a, corresponding respectively to paths of feed of these wires a, are formed in a peripheral surface of each feed roller 117, and the wires a are fitted at their lower portions in these grooves 117a, respectively, and therefore will not be displaced in a direction of the row of the wires.
On the upper side of the wires a, a plurality of press rollers 116a, corresponding respectively to the wires a, are mounted respectively on air cylinders 116 so as to move upward and downward, and when each press roller 116a is moved downward a predetermined amount, it cooperates with the lower-side feed roller 117 to hold the associated wire a therebetween. A drive device 118, comprising a servo motor M, a rotary encoder E and a speed reducer D, is connected to the feed rollers 117.
Each of the feed rollers 117 is driven by the servo motor M of the drive device 118, and when feeding the wires a, the wires a are pressed respectively by the upper-side press rollers 116a, and the length of the wires is adjusted by a method in which the revolution number and position of each feed roller 117 are detected by the rotary encoder E mounted on the servo motor M, and these detection values are transmitted to a servo amplifier Am, and an instruction indicative of the feed amount is fed from the servo amplifier Am to the servo motor M.
Such a wire feed mechanism, though simple in construction, has advantages that it is quick in response, and that a control system is stable.
However, the above feed mechanism can not absorb a variation in the rate of slip of the wires a relative to the feed rollers 117 and a variation in the outer diameter of the wires a fed from the preceding step, and these variations are directly reflected on the feed amount, thus inviting a drawback that the high-precision feed can not be achieved.
If the feed amount is too large, end portions of the wires a, fed to the connector C of the wire harness W (FIG. 10), are not properly received in the connector C, but are extended outwardly therefrom, and when fitting the lid T on the connector C, the extended portions of the wires a prevent the lid T from being fitted on the connector C. In contrast, if the feed amount is insufficient, the wires a fail to reach grooves in press-connecting terminals mounted in the connector C, and as a result the press-connection of the wires to the respective terminals can not be effected, and even if the wires only slightly reach the grooves, an insufficient mechanical strength of the press connection or other defect is encountered.